Evaluation of the Global S-Entropy Production in Membrane Transport of Aqueous Solutions of Hydrochloric Acid and Ammonia.

Kornelia M Batko,Andrzej Ślęzak

doi:10.3390/e22091021

Abstract

The results of experimental studies of volume osmotic fluxes () and fluxes of dissolved substances () in a system containing a synthetic Nephrophan® membrane (Orwo VEB Filmfabrik, Wolfen, Germany) set in a horizontal plane are presented. The membrane separated water and aqueous HCl or ammonia solutions or aqueous ammonia and HCl solutions. It was found that for the homogeneity conditions of the solutions and depend only on the concentration and composition of the solutions. For concentration polarization conditions (where concentration boundary layers are created on both sides), and depend on both the concentration and composition of the solutions and the configuration of the membrane system. The obtained results of the and flux studies were used to assess the global production of entropy for the conditions of homogeneity of solutions (), while and —to assess the global production of entropy for concentration polarization conditions ). In addition, the diffusion-convective effects and the convection effect in the global source of entropy were calculated. The concentration polarization coefficient was related to modified concentration Rayleigh number, e.g., the parameter controlling the transition from non-convective (diffusive) to convective state. This number acts as a switch between two states of the concentration field: convective (with a higher entropy source value) and non-convective (with a lower entropy source value). The operation of this switch indicates the regulatory role of earthly gravity in relation to membrane transport.

Highlights

Membrane transport processes belong to the group of basic phenomena occurring at the level of organization of physicochemical systems, in which the membrane constitutes a selective barrier separating the interior of the system from its surroundings [1,2,3]
The results of the volume osmotic flux tests for the concentration polarization conditions of the solutions separated by the membrane are shown in Figures 2 and 3
If ζk takes values in the range ζk < ζrk ≤max, the state of gravitational convection occurs in the membrane system

Summary

Introduction

Membrane transport processes belong to the group of basic phenomena occurring at the level of organization of physicochemical systems, in which the membrane constitutes a selective barrier separating the interior of the system from its surroundings [1,2,3]. The flows resulting from the action of these forces, such as diffusion or osmosis, modify the physical fields, an example of which in the case of the concentration field is concentration polarization [5,6,7,8]. This modification consists in minimizing the concentration gradients, which results in minimizing, inter alia, the osmotic and diffusion fluxes of dissolved substances and the membrane potentials [8,9]. In the case of a biological cell, the membrane plays the role of a receiver and regulator of environmental signals [10]

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Conclusion